Problem 658. Find the biggest empty box

You are given a matrix that contains only ones and zeros. Think of the ones as columns in an otherwise empty floor plan. You want to fit a big square into the empty space (denoted by zeros). What is the largest empty square sub-matrix you can find in the given matrix? You will return the row and column extent of the sub-matrix. The answer may not be unique. We will test that your sub-matrix is square, that it is empty, and that it contains the correct number of elements.

Example:

Input a = [ 1 0 0
0 0 0
0 0 0 ]

Output si = [ 2 3 2 3 ]

That is, the square indices are a(2:3,2:3). We verify that sum(sum(a(2:3,2:3))) is zero, and that it has four elements.

Solution Comments

@Informaton: Oh, it's nothing; just a cheating script ("gaming the test suite answers") combined with the well-known 'regexp' trick. A proper small solution was first submitted by Tim (Solution 97452 - size:51) and was later optimized in size by Alfonso Nieto-Castanon (Solution 181060 - size:48). My alternative Solution 1198643 (size:63), which uses for-loops instead of conv2 or filter2 function, is also much better than this 'regexp' cheat.